1. Field of the Invention
The present invention relates to a transmission apparatus that recovers from a fault occurred in a communication line, by automatically diagnosing the fault and by taking recovery measures against the fault.
2. Description of the Related Art
Conventionally, a transmission apparatus on a transmission path is provided with a plurality of transmission devices, and a controlling and monitoring unit that controls operation and monitors operating status of the transmission devices. FIG. 7 is a block diagram of a conventional transmission device and a conventional controlling and monitoring unit. The transmission device 1100 is one of a plurality of transmission devices constituting the conventional transmission apparatus. The transmission device 1100 receives an optical signal from the transmission path, converts the optical signal into an electric signal, converts the electric signal into an optical signal, and transmits the optical signal to the transmission path.
The transmission device 1100 includes a resetting unit 1111, a control FPGA 1112, an O/E converting unit 1113, a main signal terminating unit 1114, and an E/O converting unit 1115. The resetting unit 1111 applies a resetting signal to the control FPGA 1112. Upon receiving the resetting signal, the control FPGA 1112 resets the O/E converting unit 1113, the main signal terminating unit 1114, and the E/O converting unit 1115 by a controlling circuit 1112a. The control FPGA 1112 includes a programmable LSI and controls operations of the O/E converting unit 1113, the main signal terminating unit 1114, and the E/O converting unit 1115 in response to instructions from a controlling and monitoring unit 2000 that is connected to the transmission device 1100. For the control FPGA 1112, not only an FPGA but also an application specific integrated circuit (ASIC) that can be designed according to the use thereof may be employed.
The O/E converting unit 1113, the main signal terminating unit 1114, and the E/O converting unit 1115 are circuits for main signal transmission. A main signal is input into the transmission device 1100 from an external transmission path or another transmission device. The main signal is converted by the O/E converting unit 1113 from an optical signal into an electric signal, which is received by the main signal terminating unit 1114. The main signal terminating unit 1114 transmits the electric signal to the E/O converting unit 1115, which converts the electric signal into an optical signal and outputs the optical signal to an external transmission path or another transmission device.
FIG. 8 is a block diagram of a conventional transmission apparatus. The transmission apparatus includes the transmission device 1100 for an active line, and a transmission device 1200 identical to the transmission device 1100 for a standby line. Each transmission device is connected with the same controlling and monitoring unit 2000. At the startup of the transmission apparatus, the resetting units 1111 and 1211 send reset signals to other functional units 1112 to 1115 and 1212 to 1215, respectively. Upon receiving the reset signals, the control FPGAs 1112 and 1212 make settings in the main signal transmission circuits (1113 to 1115 and 1213 to 1215). After the settings, the transmission device 1100 for the active line starts the transmission of the main signal.
When the transmission is interrupted due to a fault occurred in the transmission device 1100 for the active line, the controlling and monitoring unit 2000 detects the interruption and switches the transmission device for the main signal to the transmission device 1200 for the standby line. After the switching, the main signal is transmitted by the transmission device 1200 for the standby line. Alternatively, the controlling and monitoring unit 200 may be provided externally, and may detect the fault and execute the resetting and the switching through a remote control (see, for example, Japanese Patent Application Laid-Open No. 1994-318107).
However, in the conventional technology, the main signal is transmitted only on the standby line after a fault has occurred in the active line. Therefore, if another fault occurs in the standby line, the transmission of the main signal is completely stopped (known as “deuteropathy”).
Furthermore, when a fault occurs, a service person (such as a customer service staff member) has to come to the site where the transmission apparatus is installed. As a result, it takes long until the transmission device with the fault is replaced by the service person, thereby extending the time period during which only the standby line is available, and therefore easily leading to a network down because no redundant configuration can be employed.
Furthermore, if the transmission device with the fault includes a plurality of circuits 1113 to 1115 as the transmission device 1100 shown in FIG. 7, it also takes long to locate the point at which the fault has occurred, thereby hindering the prevention of the reoccurrence of the fault.